The present invention is related to a clutch for coupling a car door of an elevator car with a landing door of an elevator system.
A conventional elevator system comprises two different sets of doors, i.e. car doors and landing doors. In general, each car of the elevator system includes at least one car door. Within each landing zone of the elevator system, at least one landing door is installed. Each landing door is located such that, when the car is stopped within the corresponding landing zone, the landing door is adjacent to a car door so that the interior of the elevator is accessible through the landing door and the car door provided that both doors are open. Under normal conditions, the landing doors are kept closed whenever the car is not present in the related landing zones. Instead of having actuators for each of the landing doors, a particular landing door can be coupled with the car door by means of a clutch that is arranged at the car door. If access to the elevator car through a particular landing door and a particular car door is desired, the elevator car is moved into the landing zone corresponding to that landing door and stopped. In addition, the car door is mechanically coupled with the landing door by means of the clutch when the car enters the landing zone. Afterwards, the landing door and the car door can be opened or closed by means of an actuator that is linked to the car door. Prior to moving the car to another landing door, the clutch is released, thereby uncoupling the car door and the landing door.
In general, the clutch is arranged at the car door and comprises at least one coupling element, which is movable with respect to the car door between a first position and a second position such that the coupling element engages with the landing door, when the elevator car is within a landing zone and the coupling element is moved towards the second position, thereby establishing the coupling of the car door with the landing door. For uncoupling the car door and the landing door, the coupling element is moved towards the first position.
For actuating the clutch, two different concepts are known. In a first concept, the clutch is linked to the actuator which drives the car door. Thus, the coupling element of the clutch and the car door are simultaneously driven by means of a single actuator. In a second concept, two actuators are provided, one of said actuators being dedicated for driving the clutch and the other actuator being dedicated for driving the car door. The latter concept is advantageous in that it allows more freedom in the timing and synchronization of movement of the coupling element since the actuation of the clutch is independent of the actuator that drives the car door.
In European patent document EP 0 676 360 A1, a clutch for coupling a car door of an elevator car with a landing door of an elevator system is disclosed. The car door is movable with respect to the elevator car by means of a first actuator. The clutch comprises a coupling element and a second actuator. The coupling element is movable with respect to the car door between a first position and a second position by means of a second actuator such that the coupling element engages with the landing door, when the elevator car is within a landing zone and the coupling element is moved towards the second position, thereby establishing the coupling of the car door with the landing door. In particular, the coupling element consists of two vanes that are connected by means of a movable linkage. By means of the second actuator, the vanes are movable with respect to each other for establishing a mechanical contact of the vanes with rollers, which rotate about horizontal axles disposed at the top of the landing door, and which provide rotationally stiff coupling. As the second actuator, a solenoid acting on an armature against the bias of a spring is used. The armature is arranged in parallel with respect to the vanes and in a sliding contact with one of the vanes. By activating the solenoid, the armature can be moved, thereby causing a movement of the vanes perpendicular to the direction of movement of the armature so that the distance between the vanes is changed. In order to control the movement of the vanes, a bias is applied on the vanes by means of a compressed spring being connected with both vanes. This clutch has several disadvantages. The sliding contact between the armature and one of the vanes is subjected to wear, thus limiting the lifetime and the reliability of operation of the clutch. In addition, the actual position of the vanes is influenced by the balance of at least four forces, i.e. the forces being provided by the solenoid and two springs and the friction between the armature and one of the vanes. Thus, it is difficult to control the motion of the vanes precisely and to ensure a given accuracy of control over a long time. In addition, due to the bias of the springs, the operation of the second actuator is not very efficient since the force generated by means of the solenoid must compensate the spring forces.
In French patent document FR 2827266, a clutch for coupling a car door of an elevator car with a landing door of an elevator system is disclosed, the clutch being independently driven by means of a DC motor whereas the car door is opened or closed by means of a separate actuator. The force provided by the DC motor is transmitted to movable parts of the clutch by means of a gear or a screw drive. Due to friction in the gear or in the screw drive, a major part of the energy provided by the DC motor is lost. Thus, the efficiency of the clutch is reduced. Furthermore, if electric power is not available for driving the DC motor, it is difficult to operate the gear or the screw drive and, thus, it becomes difficult to actuate any component of the clutch. This is disadvantageous during the installation of the clutch in the elevator system. In the case of a power failure during operation of the elevator system, it may be necessary to manually operate the clutch. It is difficult or even impossible to exercise this task, depending on the friction in the gear or the screw drive.